JP7843784B2 - Quick nozzle replacement system for atomizers - Google Patents

Description

This invention relates to the production of metal powders, and more particularly to the production of metal powders by micronization for additive manufacturing. The invention also relates to equipment for producing steel powders, and more particularly to nozzles used in the micronization process.

It is known that molten steel can be pulverized to produce metal powder. The molten metal is atomized into fine metal droplets by forcing it into a nozzle under pressure and impacting it with a jet of fluid. The fluid is either a liquid (e.g., water) or a gas (e.g., nitrogen, argon, air, or any other suitable gas). As the fluid exits the nozzle, it strikes the metal flow, generating turbulence, which results in the formation of droplets, which then solidify in the form of metal powder. The powder is then collected for further processing.

The nozzle is a crucial part of the pulverization equipment. Because nozzles are exposed to extreme conditions, they can experience wear during manufacturing or become clogged during the process.

Nozzle wear and potential clogging are limiting factors to the length of the pulverization motion. This leads to productivity and cost issues.

The object of the present invention is to address the aforementioned productivity problems by providing a nozzle assembly designed to be replaced without significantly reducing the productivity of pulverization, and a method for changing the nozzle system during the continuous production of metal powder by pulverization.

This invention provides a method for rapidly replacing nozzle assemblies by providing replacement nozzles that can be replaced in-situ during manufacturing, using a sliding nozzle assembly system. The invention further relates to an apparatus for carrying out the aforementioned method.

The object of the present invention is achieved by providing the nozzle assembly according to claim 1, which optionally includes the features of claims 2 to 9. The nozzle assembly is designed for use with the support structure according to claim 10 and optionally includes the features of claims 11 to 15.

Here, the present invention will be described in detail with reference to the attached figures, and will be explained by example without introducing any limitations. However, for clarity, please note that the pulverization tower is shown only in Figure 1 and not in the subsequent figures.

This is a schematic diagram of a pulverization device. This is a front perspective view of a nozzle system replacement device according to one embodiment of the present invention. This is a bottom perspective view of a nozzle replacement device according to one embodiment of the present invention. The support structure does not have a bottom plate in Figure 3a, but this bottom plate is present in Figure 3b. This is a bottom perspective view of a nozzle replacement device according to one embodiment of the present invention. The support structure does not have a bottom plate in Figure 3a, but this bottom plate is present in Figure 3b. This is a cross-sectional front perspective view of a nozzle replacement device according to one embodiment of the present invention, along axis I-I in Figure 2. This is a top perspective view of a nozzle assembly according to one embodiment of the present invention. This is a bottom perspective view of a nozzle assembly according to one embodiment of the present invention. This is a cross-sectional view of a nozzle assembly according to one embodiment of the present invention, taken along axis II-II in Figure 5. This is a cross-sectional view of Figure 5 along axis II-II relating to a nozzle assembly having the upper part of a support structure according to one embodiment of the present invention.

In the following description and claims, the orientation of various parts is defined according to the usual orientation of a downward pulverizer, in which the liquid metal reservoir is located above the pulverization chamber, and the heaviest portion of the coarsest pulverized powder is collected at the bottom of the pulverization column by the natural effect of gravity. Therefore, the directional terms "top," "up," "upper," "above," "bottom," "low," "lower," "below," etc., should be understood according to the aforementioned typical configuration of the pulverizer. However, the present invention can be applied regardless of the actual mounting orientation of the pulverizer, and the directional terms used in the present description and claims should simply be replaced with the orientation of the functioning pulverizer. In the accompanying drawings, the top and bottom are indicated by the arrows "T" and "B," respectively.

"Approximately parallel" or "approximately perpendicular" means a direction that cannot deviate by more than 15° from the parallel or perpendicular direction.

The terms "upstream" and "downstream" refer to the relative positions of two elements in a given direction, where the upstream element is positioned in front of the downstream element when moving in the given direction.

The term "containment" refers to a configuration in which one element (the containing element) completely covers or surrounds another element (the contained element).

The term "continuous," when applied to a surface, defines two surfaces that are in contact with each other over at least a portion of the surface. The term "continuous," when applied to a volume, defines two volumes having continuous surfaces.

"Fire-resistant" materials refer to materials that are resistant to decomposition by heat, pressure, or chemical attack, and that maintain their strength and shape at high temperatures.

The terms "high pressure" and "low pressure" refer to the amount of pulverizing fluid pressure used in a given pulverization process. "High pressure" refers to the pressure level required to supply the pulverizing fluid nozzle in order to reach the desired spray fluid pressure exiting the nozzle. "Low pressure" refers to the pressure level required to supply the pulverizing fluid nozzle in order to reach positive pressure at the nozzle outlet.

Referring to Figure 1, a general overview of the pulverization device 100 is shown first.

Molten metal 109, such as steel, aluminum, titanium, or any other metal or metal alloy, is pulverized into fine metal droplets by being forced into nozzle 1 under pressure and by impacting it with a jet of fluid supplied from fluid supply unit 105 via supply circuit 106. The fluid, upon exiting nozzle 1, strikes the metal flow and enters pulverization tower 102, generating turbulence, which results in the formation of a spray 110 made of metal droplets, which then solidifies in the form of metal powder. The powder is then collected for further processing.

At this stage of the explanation, it should be noted that the term “nozzle” generally refers to the device through which liquid metal passes as it enters the pulverization tower. The following description of the apparatus according to the present invention will describe the “nozzle” in more detail, including several different parts that together form the “nozzle assembly” and the “nozzle replacement device.”

The molten metal 109 is held in a liquid metal reservoir 101 having a reservoir opening 104 at its bottom, and the liquid metal can flow into the nozzle 1 through the reservoir opening. For example, the liquid metal reservoir is equipped with a channel 103 through which the liquid metal is forced to exit the reservoir 101 via the reservoir opening 104. This channel 103 may be equipped with an inductor to control the temperature of the liquid metal exiting through the reservoir opening 104.

The pulverization tower 102 is typically filled with an inert gas to prevent the powder from oxidizing. The metal droplets are cooled as they fall into the pulverization tower.

The micronizing fluid can be a liquid or a gas. Generally speaking, gas micronization is advantageous for producing powder particles with high roundness. The particles are also less susceptible to oxidation than, for example, those produced by water micronization. On the other hand, liquid micronization, particularly water micronization, can offer a good balance of cost, productivity, and quality when the required particle size and shape for the aforementioned applications are permitted.

In gas pulverization, the pulverizing gas is preferably argon or nitrogen. Helium can also be used, but due to its high thermal conductivity, significant overheating (above 300°C) is required to avoid clogging. Both of these gases increase the melt viscosity more slowly than other gases, such as helium, thereby promoting the formation of smaller particle sizes. They play a role in controlling the purity of the chemical properties, avoiding undesirable impurities, and ensuring a good form of powder. Since the molar weight of argon is 39.95 g/mol compared to 14.01 g/mol of nitrogen, finer particles can be obtained by using argon than by using nitrogen. On the other hand, the specific heat capacity of argon is 0.52 J/(gK) compared to 1.04 J/(gK) of nitrogen. Therefore, nitrogen increases the cooling rate of the particles. Argon may be preferred over nitrogen to avoid contamination of the composition by nitrogen, and when the chemical properties of the molten material are reactive.

The gas flow affects the particle size distribution and microstructure of the metal powder. In particular, faster flow rates result in higher cooling rates. Therefore, the gas-to-metal ratio, defined as the ratio of gas flow rate (kg/h) to metal flow rate (kg/h), is preferably maintained between 1 and 5, more preferably between 1.5 and 3.

The outlet diameter of the liquid metal nozzle affects the flow rate of the molten metal, and therefore the particle size distribution and cooling rate. The maximum diameter is limited to 6 mm, for example, to limit the increase in average particle size and the decrease in cooling rate. A diameter of 2-3 mm is more preferable to more precisely control the particle size distribution and promote the formation of the desired microstructure.

The metal powder obtained by micronization can be classified so that particles of a size better suited to the technology, particularly additive manufacturing technology, are maintained for later use. For example, in the case of additive manufacturing by powder bed fusion, a range of 15 to 50 μm is preferred. In the case of additive manufacturing by laser metal deposition or direct metal deposition, a range of 45 to 150 μm is preferred.

The shape and size of the liquid metal nozzle outlet are crucial for ensuring the production of metal powder with good quality. However, during the pulverization process, the nozzle outlet undergoes significant wear due to the pressure of the liquid metal applied to the outlet, the high temperatures imposed by the liquid metal (e.g., over 1500°C in the case of steel), and the chemical interactions that can occur between the liquid metal nozzle material and the liquid metal. To perform a continuous pulverization process at a stable product quality level, it is necessary to change the liquid metal nozzle during operation. Since the pulverization process depends on the liquid metal passing through the nozzle, the nozzle change operation itself temporarily interrupts the pulverization process. Therefore, this operation must be performed as quickly as possible. Furthermore, since the liquid metal exits through the reservoir opening under pressure, the flow of liquid metal must be controlled during the nozzle change operation for safety and equipment protection purposes (the pulverization tower, in particular, can be damaged by liquid metal leakage).

Figures 2 to 4 show a nozzle replacement device 30 according to one embodiment of the present invention. This device allows for rapid movement of the nozzle to extend and retract it into a predetermined position for quick replacement.

The nozzle replacement device 30 comprises the following elements.
- At least one nozzle assembly 10
- Support structure 20 intended to hold the nozzle assembly 10
- A high-pressure pulverizing fluid supply unit 106 and a distribution circuit 105 (not shown) suitable for supplying high-pressure pulverizing fluid for the pulverization process.
- A mechanical device designed to move the nozzle assembly 10 within the support structure in a direction S substantially parallel to the liquid metal reservoir opening 104. The mechanical device is not shown in the accompanying drawings.

The support structure 20 is configured such that the nozzle assembly 10 can move within the support structure 20 in a direction S substantially parallel to the liquid metal reservoir opening 104, and the support structure comprises the following:
- A portion of the support structure 20 corresponding to a portion of the nozzle assembly 10i having a liquid metal inlet effectively aligned with the reservoir opening. Referring to Figure 2, the portion in use is roughly demarcated by dotted lines i1 and i2.
- Considering the direction of movement S of the nozzle assembly, the inlet section 20e corresponds to the portion of the support structure 20 located upstream of the section 20i in use.

For clarity, the sliding direction S in the attached drawings is shown as a linear direction, and the overall shape of the support structure 20 is a linear shape. However, it is also possible to carry out the present invention using a curved support structure 20 and an associated curved sliding direction S. Such a curved design may be desirable, for example, to design a support structure 20 that fits an allocated volume 20, or more generally, to reduce the overall space occupied by the nozzle exchange device 30.

Referring to Figures 4 to 8, the nozzle assembly 10 comprises the following elements.
- An upper part 11 is designed to be located closest to the liquid metal reservoir during the pulverization spraying process, and the upper part has an upper surface 12.
- A bottom 19 designed to be located closest to the pulverization tower during the pulverization process, the bottom having a bottom surface 18.
- When considering the sliding direction S, the upper surface and the lower surface are joined together, and the upstream surface and downstream surface are located on the upstream and downstream sides of the nozzle assembly, respectively.
A liquid metal nozzle 40 having a liquid metal inlet 41 suitable for alignment with a reservoir opening 104 and a liquid metal outlet 42 configured to pour out a liquid metal flow in a pulverization tower, wherein the liquid metal inlet 41 is located on the upper surface 12 and the liquid metal outlet 42 is located on the bottom surface 18.
A pulverizing fluid nozzle 50 having at least one pulverizing fluid inlet 51 and a pulverizing fluid outlet 52 configured such that a fluid flowing through a pulverizing fluid outlet 52 collides with a liquid metal flowing from a liquid metal outlet 42, wherein the pulverizing fluid outlet 52 is located on the bottom surface 18.
The nozzle assembly 1 is adapted to be attached to the support structure 20 in such a manner that the nozzle assembly 1 can move within the support structure 20 in a direction S substantially parallel to the liquid metal reservoir opening 104.

Referring to Figure 2, in order to replace nozzle assembly 1 during manufacturing, a mechanical device (not shown in the figure) pushes nozzle assembly 1, resulting in the nozzle assembly 10i being pushed out of the section 20i and replaced by the next inline nozzle assembly 10n, located in the inlet section 20e at the closest position to the section 20i. This movement can be performed in a very short time, for example, less than 5 seconds, or even more preferably less than 2 seconds or less than 1 second, so that the liquid metal flow is hardly disturbed and the productivity loss associated with nozzle replacement is very small.

In certain embodiments, the upstream surface 14 and the downstream surface 15 have complementary shapes, ensuring a continuous upper surface 12 between two consecutive liquid metal nozzle inlets 41 of two nozzle assemblies 10, where the respective downstream and upstream surfaces are positioned opposite each other.

For clarity, all nozzle assemblies 10 shown in the attached figures have a substantially cubic shape. Their upstream surface 14 and downstream surface 15 are flat, straight surfaces. However, other shapes can be used to carry out the present invention. For example, it is possible to use curved surfaces for the upstream and downstream planes while maintaining the same radius of curvature to ensure the required shape complementarity. This type of design can advantageously allow two consecutive nozzle assemblies within a support structure to rotate slightly even when one is pressed against the other. This can be advantageous when using a support structure having a substantially nonlinear shape related to a curved sliding direction S. Advantageously, the above-described design of the nozzle assembly 10 ensures that during a nozzle change operation, the nozzle assembly in use 10i and the next inline nozzle assembly 10n come into contact with each other on their vertical sides, thereby ensuring that the top surface 12 of the nozzle assembly forms a continuous surface that blocks the metal flow during the nozzle change operation, so that there is no harmful liquid metal leakage within the pulverization tower. This means that it may be possible to perform a nozzle change operation without requiring specific devices such as stopper rods to stop the metal flow. Furthermore, the nozzle replacement device can even be used to intentionally temporarily halt the metal flow when it is necessary to do so for industrial reasons, such as when certain operations need to be performed on the pulverization tower or when there are production problems related to any of the pulverization equipment. To temporarily halt the metal flow, the nozzle assembly in use 10i is partially pushed out from the section in use 20i, and the next inline nozzle assembly 10n is partially pushed inward from the section in use so that the reservoir opening is blocked by the upper surface 12 of either or both of the nozzle assembly in use 10i or the next inline nozzle assembly 10n.

In specific embodiments, as shown in Figures 5 to 8, the pulverizing fluid inlet 51 of the nozzle replacement assembly 10 is located in a different plane from the liquid metal inlet 41. Advantageously, this allows for independent management of the connections to the liquid metal inlet and the pulverizing fluid inlet, each requiring good airtightness for a smooth pulverization process. For nozzles 10i in use, the liquid metal inlet 41 needs to be precisely aligned with the reservoir opening 104. Meanwhile, the pulverizing fluid inlet 51 needs to be fluid-tightly connected to the pulverizing fluid supply unit 106 (especially since the pulverizing fluid pressure can be very high). If both the liquid metal inlet and the pulverizing fluid inlet are located in the same plane, there is no freedom to independently adjust their positions and access them independently. However, if they are located in separate planes, it is possible to provide a quick-fit system for the pulverizing fluid inlet 51, for example, as shown in the accompanying figures. The pulverizing fluid inlet 51 can be easily accessed independently from the top surface 12 of the nozzle assembly.

According to a particular embodiment of the present invention, each nozzle assembly 1 has an even number of pulverizing fluid inlets 51 forming at least one pair of pulverizing fluid inlets, wherein for each pair, the inlets are located on substantially parallel surfaces on opposite sides of the nozzle assembly 1, on substantially opposite sides. Advantageously, this configuration allows for a better distribution of the pulverizing fluid flow within the pulverizing spray nozzle 50.

According to specific embodiments of the present invention, as shown in Figures 5 to 8, the pulverization fluid outlet 52 is substantially annular in shape. Advantageously, this allows for a homogeneous pulverization fluid flow that collides with the liquid metal flow within the pulverization chamber.

According to a specific embodiment of the present invention as shown in Figures 5 to 8, the upper part 11 of each nozzle assembly 10 comprises an upper plate 13 made of a refractory material, the upper plate 13 housing a portion of the liquid metal nozzle 40 located within the upper part 11. Advantageously, the use of a refractory material allows for good resistance to the high temperatures typically experienced by the apparatus during the pulverization process, and also provides good resistance to any resulting liquid metal flow that may strike the upper plate 13 during nozzle replacement operations, when using a nozzle replacement device to temporarily stop the liquid metal flow, or when parasitic liquid metal leaks. Furthermore, the design in which the upper plate 13 houses the liquid metal nozzle 40 allows for easy maintenance and assembly of the upper part 11, enables good airtightness of the upper part, and thus prevents damage to the nozzle assembly due to liquid metal leakage during nozzle replacement operations, or allows the use of the nozzle assembly to temporarily stop the metal flow, or generally prevents damage during pulverization operations.

According to a particular embodiment of the present invention, the portion of the upper plate 13 comprising the upper surface 12 is surface-treated to reduce its coefficient of friction. Advantageously, this allows the nozzle assembly 10 to slide smoothly within the support structure 20, minimizing wear on both the nozzle assembly 10 and the support structure 20 during nozzle replacement operations.

According to a particular embodiment of the present invention, the upper plate 13 is made of graphite. Graphite is both a refractory and low-friction material, which provides the aforementioned advantages of good resistance to liquid metals and general environmental heat, as well as less wear on the nozzle assembly and support structure during nozzle replacement operations.

According to a particular embodiment of the present invention as shown in Figures 5 to 8, the bottom 19 comprises a pulverizing fluid nozzle 50 designed to accommodate a portion of a liquid metal nozzle 40 located within the bottom 19. Advantageously, this allows for easy maintenance and assembly of the bottom 19 and ensures good airtightness of the bottom. This design also makes it possible to provide a nozzle assembly in which the pulverizing fluid nozzle 50 can be reused after the nozzle has been pushed out during use. In fact, it is possible to remove the used liquid metal nozzle 40 from the pulverizing fluid nozzle 50 because the liquid metal nozzle is simply inserted into an interior provided to accommodate the volume of the pulverizing fluid nozzle 50. This is advantageous in terms of maintenance and operating costs, as the pulverizing fluid nozzle is an expensive device. For example, the pulverizing fluid nozzle 50 is made of stainless steel and, as described above, is provided with a quick-fit inlet. For example, the pulverizing fluid nozzle is made of a top and bottom that are assembled together, for example, by screwing them together, as shown in Figure 7. Advantageously, this allows for complex part designs while still utilizing conventional part manufacturing processes, such as casting. This two-part configuration also advantageously facilitates easy assembly of the liquid metal nozzle 40 and the pulverizing fluid nozzle 50 before use and easy disassembly after use.

According to a particular embodiment of the present invention, as shown in Figures 4 and 8, the support structure 20 includes an upper part 21 designed to be continuous with the upper surface 12 of the nozzle assembly 10, and the working portion 21i of the upper part includes the following:
- An intermediate liquid metal nozzle 22, configured to be connected at its upper end 23 to the reservoir opening 104 and at its bottom end 24 to the liquid metal inlet 41 of the nozzle assembly 10i in use.
- Upper plate 25 housing the intermediate liquid metal nozzle 22

In fact, this embodiment allows the nozzle through which the liquid metal flows to be separated into two distinct parts: an intermediate nozzle 22, which is a non-movable part integrated within the support structure 20, and a liquid metal nozzle 40 of the nozzle assembly 10, which can be easily replaced during the pulverization operation thanks to the nozzle replacement operation described above. Advantageously, this allows for easy replacement of the most critical part of the nozzle, which is the liquid metal outlet 42, while simultaneously avoiding contact between the movable part of the nozzle and the reservoir opening 104, which would result in wear on the reservoir opening and related parts of the liquid metal reservoir 101, such as the channel 103. Furthermore, by providing an upper plate 25 that houses the intermediate liquid metal nozzle 22, it becomes possible to pull out and replace the intermediate liquid metal nozzle 22 after the pulverization operation is complete, ensuring good airtightness and stability of the apparatus.

According to a particular embodiment of the present invention, the upper plate 25 of the in-use section of the support structure is made of a fire-resistant material. Advantageously, this allows for good resistance to the typical high temperatures the apparatus experiences during the pulverization process, and also good resistance to liquid metal flow that may result from parasitic liquid metal leakage.

According to a particular embodiment of the present invention, the bottom surface 26 of the portion of the upper plate 25 of the support structure in use is surface-treated to reduce its coefficient of friction. Advantageously, this allows the nozzle assembly 10 to slide smoothly within the support structure 20 in use section 20i, minimizing wear on both the nozzle assembly 10 and the support structure 20 during nozzle replacement operations.

According to a particular embodiment of the present invention, the upper plate 25 of the in-use section of the support structure is made of graphite. Graphite is both a refractory and low-friction material, which provides the aforementioned advantages of good resistance to liquid metal and general environmental heat, as well as less wear on the nozzle assembly and support structure during nozzle replacement operations.

According to a specific embodiment of the present invention as shown in Figures 2 to 4, the support structure 20 further comprises a bottom 29 configured to support the bottom 19 of the nozzle assembly 10. Advantageously, this allows for better mechanical stability of the nozzle exchange device, as the nozzle assembly is supported from the bottom.

According to a particular embodiment of the present invention, the nozzle replacement device 30 further comprises a low-pressure fluid supply unit and a distribution circuit (not shown in the accompanying figures),
- At least the following inline nozzle assembly 10n has at least one of its pulverizing fluid supply inlets connected to the low-pressure fluid supply unit,
- The nozzle assembly 10i in use has at least one of its pulverizing fluid supply inlets connected to the high-pressure pulverizing fluid supply unit.

By connecting the next inline nozzle assembly 10n to the low-pressure fluid circuit, positive pressure is ensured at the pulverizing fluid outlet 52 of the next inline nozzle assembly 10n. Advantageously, this generally protects the pulverizing fluid outlet 52 and the pulverizing fluid nozzle 50 from contamination by suspended metal powder particles that may be present in the pulverization tower. In fact, it is known that very small diameter metal particles, such as those with a diameter of less than 5 micrometers, can fly around in the pulverization tower and are not easily captured by the appropriate equipment of the pulverization tower. These suspended particles can clog and damage the pulverizing fluid nozzles, impairing their good function when in use and making them more difficult to reuse in subsequent runs without cleaning or maintenance. Using low-pressure fluid to prevent metal powder contamination advantageously utilizes the existing fluid inlet 52, avoids wasting expensive high-pressure fluid for this purpose, and ensures that no negative interaction occurs between the fluid exiting the next inline nozzle assembly 10n and the high-pressure fluid exiting the nozzle assembly 10i in use.

According to a particular embodiment of the present invention, the fluid used in the low-pressure fluid supply and distribution circuit is the same fluid as the pulverizing fluid. Advantageously, this optimally utilizes the existing fluid circulation chambers of the fluid inlet 52 and the pulverizing fluid nozzle 50. In fact, these are configured for the flow of the pulverizing fluid.

According to a particular embodiment of the present invention, the low-pressure fluid supply unit includes at least a portion of the recirculated pulverizing fluid recovered after being depressurized by use in the pulverizing process. Advantageously, using available spent pulverizing fluid can provide cost and efficiency benefits.

According to a particular embodiment of the present invention, at least the nozzle assembly in use 20i and the subsequent in-line nozzle assembly 20n are connected to both high-pressure and low-pressure circuits, and the nozzle exchange device 30 further comprises a valve system for each nozzle assembly to switch between the low-pressure and high-pressure circuits of each nozzle assembly. Advantageously, this allows the implementation of the aforementioned low-pressure fluid injection system to prevent metal powder contamination without the need to manage the fluid supply connection during nozzle exchange operations, and the fluid supply section of the new nozzle in use 10i is switched to the high-pressure fluid supply section during nozzle exchange operations by operating the valve system.

According to a particular embodiment of the present invention, the nozzle exchange device 30 further comprises a linear actuator designed to switch the fluid supply to the nozzle assembly fluid inlet 51 between a high-pressure circuit and a low-pressure circuit. Advantageously, this allows the same set of fluid inlets 51 to be used for connections to both the high-pressure and low-pressure fluid supply sections, thereby simplifying the design and maintenance of the pulverizing fluid nozzle 50.

According to a particular embodiment of the present invention, the nozzle replacement device 30 further comprises a liquid metal nozzle wear detector (not shown in the accompanying figures) configured to monitor the level of material wear at the liquid metal nozzle outlet during use. Advantageously, this allows the nozzle replacement operation to be performed at an optimal time, thereby ensuring the maximum efficient use of the nozzle assembly during use without compromising the quality and productivity of the pulverization process.

According to a particular embodiment of the present invention, as shown in Figure 4, the nozzle replacement device 30 further comprises a stopper rod 108 designed to block the liquid metal flow exiting through the reservoir opening 104. For example, the stopper rod is moved downward to block the inlet of the channel 103 in order to stop the liquid metal flow. Advantageously, the presence of the stopper rod ensures the possibility of stopping the metal flow when necessary, for example, for operational reasons or to replace the nozzle. This further prevents leakage of liquid metal during nozzle replacement operations.

According to a particular embodiment of the present invention, as shown in Figure 4, the stopper rod 108 houses a hollow volume 109 and further comprises a rod opening 110 through which pressure can be applied to the liquid metal below the stopper rod to push the liquid metal remaining below the stopper rod through the liquid metal outlet 42 when the stopper rod 108 is used to stop the liquid metal flow. In fact, when the stopper rod is operated to stop the liquid metal flow, the portion of liquid metal contained within the liquid metal nozzle 40 is no longer subjected to the pressure coming from the liquid metal in the liquid metal reservoir. As a result, this stops the liquid metal from flowing through the liquid metal nozzle 40, which may lead to the freezing of the metal within the liquid metal nozzle 40, making it impossible to use the stopper rod again after it has been lifted. Furthermore, the liquid metal column may solidify further above the liquid metal nozzle 40 (for example, within the intermediate nozzle 22 or within the reservoir opening 104). This forms a solid connection of solidified metal between the nozzle assembly 10 and the support structure or liquid metal reservoir, preventing the sliding motion of the nozzle assembly 10 and thus effectively hindering the overall function of the nozzle exchange device 30. To prevent this, it is advantageous to use the aforementioned hollow stopper rod 108, which has a rod opening 110 through which pressure can be applied to the liquid metal below the stopper rod to push the liquid metal remaining below the stopper rod through the liquid metal outlet 42 when the stopper rod 108 is used to stop the liquid metal flow. For example, fluid can be blown through the rod opening 110 to apply pressure to the liquid metal column below the stopper rod in order to push out the stopper rod and prevent the aforementioned harmful solidification. For example, the stopper rod may further include an inner rod that can slide downward within a hollow volume 109, and thus compress the fluid within the hollow volume 109 to apply the pressure necessary to push out the liquid metal remaining below the stopper rod.

According to a specific embodiment of the present invention, an upward pressure is applied to the bottom 19 of the nozzle assembly 10i in use during the pulverization process, and this upward pressure is configured to counteract the downward pressure arising from the liquid metal flow. Advantageously, this ensures that the nozzle assembly 10i in use is firmly held in place during the pulverization process and does not move due to parasitic shear stress or vibration. Furthermore, this also protects the support structure. In fact, the downward pressure applied by the liquid metal flow through the liquid metal nozzle 20 results in a downward pressure applied to the support structure 20 by the nozzle assembly 10i in use. If this pressure is not compensated by intentionally applying an upward counter-pressure, the entire load of this pressure is supported by the support structure 20, potentially leading to mechanical wear, warping, deformation, and subsequent maintenance problems. Such considerations are all the more important when considering that the pulverization operation generates high temperatures, and therefore the support structure is exposed to both high temperatures and high mechanical loads, potentially leading to premature failure due to well-known phenomena such as creep.

The nozzle replacement operation for implementing the above-mentioned device consists of the following steps:
A/ The step of providing the aforementioned nozzle replacement device,
B/A step of operating a mechanical device to activate the movement of the nozzle assembly in the sliding direction S,
C/ The step of extruding the nozzle assembly in use from the in-use section of the support structure and replacing it with the next inline nozzle which will become the new nozzle in use,
It is equipped with.

The nozzle replacement operation optionally includes an additional step of switching the fluid supply to the new, in-use nozzle from a low-pressure fluid supply to a high-pressure pulverizing fluid supply. This step is performed by using a valve system, a linear actuator, or any other system suitable for rapid switching between the high-pressure and low-pressure fluid sources.

The nozzle replacement operation optionally includes an additional step of using information from a liquid metal nozzle wear detector configured to monitor the level of material wear at the liquid metal nozzle outlet in use, in order to determine the appropriate moment to activate the nozzle replacement operation.

The nozzle replacement operation optionally includes an additional step before step B described above, in which the stopper rod is moved to stop the liquid metal flow from the reservoir opening 104.

The nozzle replacement operation optionally includes an additional step before step B described above, in which pressure is applied to the liquid metal below the stopper rod to push the remaining liquid metal through the liquid metal outlet 42.

The nozzle replacement operation optionally includes an additional step after step C described above, in which upward pressure is applied to the bottom of the nozzle assembly in use.

Claims (15)

A nozzle assembly (10) suitable for use in a liquid metal pulverization process, wherein liquid metal (109) held in a liquid metal reservoir (101) and exiting the liquid metal reservoir through a reservoir opening (104) is pulverized by a pulverizing fluid to form a metal spray (110) in a pulverization tower (102), the nozzle assembly (10) is,
- An upper part (11) designed to be located closest to the liquid metal reservoir (101) during the pulverization process, the upper part (11) having an upper surface (12),
- A bottom (19) designed to be located closest to the pulverization tower (102) during the pulverization process, the bottom (19) having a bottom surface (18),
- When considering the sliding direction S, the upper surface (12) and the lower surface (18) are joined, and the upstream surface (14) and the downstream surface (15) located on the upstream and downstream sides of the nozzle assembly,
- A liquid metal nozzle (40) having a liquid metal inlet (41) suitable for alignment with a reservoir opening (104) and a liquid metal outlet (42) configured to pour out the liquid metal flow in the pulverization tower (102), wherein the liquid metal inlet (41) is located on the top surface (12) and the liquid metal outlet (42) is located on the bottom surface (18),
- A pulverizing fluid nozzle (50) having at least one pulverizing fluid inlet (51) and a pulverizing fluid outlet (52), configured such that the fluid flowing through the pulverizing fluid outlet (52) collides with the liquid metal flowing from the liquid metal outlet (42), wherein the pulverizing fluid outlet (52) is located at the bottom surface (18),
Equipped with,
The nozzle assembly (10) is adapted to be mounted on the support structure (20) in such a configuration that the nozzle assembly (10) can move within the support structure (20) in a sliding direction S parallel to the liquid metal reservoir opening (104). The nozzle assembly (10) according to claim 1, wherein the upstream surface (14) and the downstream surface (15) have complementary shapes, and these shapes connect the upper surface (12) between two consecutive liquid metal nozzle inlets (41) of two nozzle assemblies (10) having their respective upstream surfaces (14) and downstream surfaces (15) arranged to face each other. The nozzle assembly (10) according to claim 1 or 2, wherein at least one spray fluid inlet (51) is located in a plane different from that of the liquid metal inlet (41). The nozzle assembly according to any one of claims 1 or 3, having an even number of pulverizing fluid inlets (51) forming at least one pair of spray fluid inlets (51), wherein for each at least pair, the inlets (51) are located on opposite parallel surfaces on opposite sides of the nozzle assembly (10). The nozzle assembly (10) according to any one of claims 1 to 4, wherein the pulverizing fluid outlet (52) has an annular shape. The nozzle assembly (10) according to any one of claims 1 to 5, wherein the upper part (11) comprises an upper plate (13) made of a fire-resistant material, and the upper plate (13) is designed to accommodate a portion of a liquid metal nozzle (40) located within the upper part (11). The nozzle assembly (10) according to claim 6, wherein the portion of the upper plate (13) included in the upper surface (12) is surface-treated to reduce its coefficient of friction. The nozzle assembly (10) according to claim 6 or 7, wherein the upper plate (13) is made of graphite. The nozzle assembly (10) according to any one of claims 1 to 8, wherein the bottom portion (19) comprises a pulverizing fluid nozzle (50) designed to accommodate a portion of the liquid metal nozzle (40) located within the bottom portion (19). A support structure (20) designed to hold at least one nozzle assembly (10) according to any one of claims 1 to 9, suitable for use in a liquid metal pulverization process in which liquid metal (109) held in a liquid metal reservoir (101) and exiting the liquid metal reservoir through a reservoir opening (104) is pulverized by a pulverizing fluid to form a metal spray (110) in a pulverization tower (102), wherein the support structure (20) is configured such that the nozzle assembly (10) can move within the support structure (20) in a direction S parallel to the liquid metal reservoir opening (104), and the support structure (20) is
- A working section (20i) corresponding to a portion of a support structure (20) designed to house a nozzle assembly (10i) in use, wherein the nozzle assembly (20i) has a liquid metal inlet (41) effectively aligned with a reservoir opening (104),
- Considering the sliding direction S, the inlet section (20e) corresponds to the portion of the support structure (20) located upstream of the section in use (20i),
A support structure (20) further comprising the above. The nozzle assembly (10) further comprises an upper part (21) designed to be continuous with the upper surface (12), the portion of the upper part (21i) in use is
- An intermediate liquid metal nozzle (22) is fitted to be connected at its upper side (23) to a reservoir opening (104) and at its bottom side (24) to a liquid metal inlet (41) of a nozzle assembly (20i) in use,
- An upper plate (25) that houses the intermediate liquid metal nozzle (22),
The support structure (20) according to claim 10, comprising: The support structure (20) according to claim 11, wherein the upper plate (25) of the section of the support structure in use is made of a fire-resistant material. The support structure (20) according to claim 12, wherein the bottom surface of the upper plate (26) of the section of the support structure in use is surface-treated to reduce its coefficient of friction. The support structure (20) according to claim 12, wherein the upper plate (25) of the section of the support structure in use is made of graphite. The support structure (20) according to any one of claims 10 to 14, further comprising a bottom (29) configured to support the bottom (19) of the nozzle assembly (10).